StateIO s a ≡ StateT s IO a

stateio.hs

{-# LANGUAGE GADTs #-}

import Control.Monad.Operational

data IStateIO s a where
    Get    :: IStateIO s s
    Put    :: s    -> IStateIO s ()
    LiftIO :: IO a -> IStateIO s a

get'    = singleton Get
put'    = singleton . Put
liftIO' = singleton . LiftIO

type StateIO s = Program (IStateIO s)

runStateIO :: StateIO s a -> s -> IO a
runStateIO = eval . view
    where
    eval :: ProgramView (IStateIO s) a -> s -> IO a
    eval (Get       :>>= is) s = runStateIO (is s) s
    eval (Put s'    :>>= is) s = runStateIO (is ()) s'
    eval (LiftIO io :>>= is) s = io >>= (\a -> runStateIO (is a) s)
    eval (Return a) s          = return a

proc :: StateIO Int ()
proc = do
    x <- get'
    liftIO' $ (putStr.show)  x
    put' 514
    y <- get'
    liftIO' $  print y

main = runStateIO proc 114
-- 114514